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STUDY OF MICROSTRUCTURES IN γ/γ'--αMo DIRECTIONAL EUTECTOID ALLOY INDUCED BY LASER RAPID MELTING SOLIDIFICATION |
JIN Tao; SUN Xiaofeng; ZHAO Nairen; LIU Jinlai; ZHANG Jinghua; HU Zhuangqi |
Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110016 |
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Cite this article:
JIN Tao SUN Xiaofeng ZHAO Nairen LIU Jinlai ZHANG Jinghua HU Zhuangqi. STUDY OF MICROSTRUCTURES IN γ/γ'--αMo DIRECTIONAL EUTECTOID ALLOY INDUCED BY LASER RAPID MELTING SOLIDIFICATION. Acta Metall Sin, 2009, 45(5): 527-535.
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Abstract The principle purpose of surface modification by laser rapid melting solidification is to improve the surface properties of materals through the change of their surface microstructures. The γ/γ'–αMo directional eutectoid alloy consisting of a chemical composition (atomic fraction) of 15.41%Al, 2.56%V, 3.25%Cr, 8.41%Mo and balance Ni was chosen in the present study. The master alloy was melted in a vacuum induction furnace, and then the directional eutectoid specimens were prepared in a vacuum solidified furnace. Two ways, i.e. pulse and scan, were used for the surface laser treatment. A finer directional eutectoid structure grows again in the melting zone when the laser pulse is parallel to the eutectoid growth direction. However, when the laser pulse is perpendicular to the eutectoid growth direction, the microstructures of melting zone are composed of much denser cell–like crystalline and dendrites. The dendritic arm in dendrite structure after laser melting consists of the γ–solid solution and the fine γ'–participites, and the microstructures in the interdendrites are composed of the γ–solid solution containing γ' and the metastable phase precipitates which are enriched by Mo. These metastable phases are the ordered [αMo(ordered)], Ni3Mo and ordered [Ni3Mo(ordered)].
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Received: 09 October 2008
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